Sunday, June 04, 2006

Felten on wiretapping without specific suspects

Ed Felten has posted the latest in his series about 21st century wiretapping and makes the interesting point that there is a case for blanket wiretapping if human access to specific elements of those communications is only triggered by narrow algorithms that identify a specific suspect's voice pattern or

"some predetermined dialog that is extremely unlikely to occur naturally. Like this, for instance:

First Speaker: The Pirates will win the World Series this year.Second Speaker: Yes, and Da Vinci Code is the best movie ever made.

The police ask us for permission to run automated voice recognition algorithms on all phone conversations, and to record all conversations that contain this verbal handshake. Is it reasonable to give permission?If the voice recognition is sufficiently accurate, this could be reasonable — even though the wiretapping is not based on advance suspicion of any particular individual. Suspicion is based not on the identity of the individuals speaking, but on the content of the communication...

Obviously we wouldn’t give the police carte blanche to use any kind of content-based suspicion whenever they wanted. What makes this hypothetical different is that the suspicion, though content-based, is narrowly aimed and is based on specific evidence. We have good reason to believe that we’ll be capturing some criminal conversations, and that we won’t be capturing many noncriminal ones. This, I think, is the general principle: intercepted communications may only be made known to a human based on narrowly defined triggers (whether individual-based or content-based), and those triggers must be justified based on specific evidence that they will be fruitful but not overbroad.

You might argue that if the individualized suspicion principle has been good enough for the past [insert large number] years, it should be good enough for the future too. But I think this argument misses an important consequence of changing technology.

Technology raises the possibility that automated algorithms can implement triggering rules, so that content-based triggers become possible — in theory at least.

Given that content-based triggering was infeasible in the past, the fact that traditional rules don’t make provision for it does not, in itself, end the argument. This is the kind of situation that needs to be evaluated anew, with proper respect for traditional principles, but also with an open mind about how those principles might apply to our changed circumstances."

It's what Larry Lessig might call a latent ambiguity. Ed's right - the technology does potentially offer new possibilities for law enforcement but only if the content filtering technology can be sufficiently refined. At the moment it is so crude as to be useless, offering so many false leads that the resources to chase down all of them just don't exist, not to mention the civil liberties implications of such an approach. The temptations for police and intelligence services to trawl (theoretically) legally no-go data warehouses, other than with specific narrow grounds of suspicion (unique content or individually targetted), especially under pressure of simplistic targets to produce results, would be too great to ignore. As Cardinal Richelieu said, give him six lines written by the most honest man and he'll find the evidence there to have him hanged - the data warehouses proposed will always contain enough to metaphorically hang someone. But the data smog gives the real bad guys so much more room for manoeuvre.